Unique Drug Combo Promising for Severe, Intractable Pain

SAN DIEGO — Low doses of the hormone oxytocin along with the anesthetic ketamine may provide a unique and effective therapeutic approach to some patients with severe, intractable pain

This therapeutic approach is "incredibly unique" and is safe and effective in some patients with intractable pain. "If you put these two together, you could replace any short-acting opiate," Caron Pedersen, FNP-C, DC, BSN, BS-PT, a nurse practitioner, chiropractor, and physical therapist specializing in patients with spinal pain, told Medscape Medical News.

Dr Pedersen has been working with pain management expert, Forest Tennant, MD, DPH, Veract Intractable Pain Clinic, West Covina, California, to find better ways to treat patients with very severe pain.

Such patients, said Dr Pedersen, "are pretty much opioid-dependent and have been for long time, and are not getting relief."

Dr Pedersen presented some of her research here at the Academy of Integrative Pain Management (AIPM) 28th Annual Meeting.

Alternative to Opioids?

A variety of antiseizure, antidepressant, and anti-inflammatory agents, as well as muscle relaxants and adrenergic blocking agents, provide mild to moderate pain relief. But these approaches are not always a substitute for opioids in patients with severe pain.

Both oxytocin and ketamine provide analgesia by mechanisms other than stimulating opioid receptors.

Produced in the hypothalamus, oxytocin is a potent natural pain reliever. The hormone is released in pregnant women during labor and also in other painful conditions or stressful events.

It has been reported to relieve pain in patients with headache, chronic back pain, and fibromyalgia, and there is "a mountain of research" on oxytocin's complex production, release, and receptor system, said Dr Pedersen.

Dr Tennant explained that some of the hormone is released into the peripheral circulation via the posterior pituitary and some into the central nervous system, including the spinal fluid.

Oxytocin receptors are found at multiple sites in the brain and throughout the spinal cord, said Dr Tennant. In addition to activating its own receptors and decreasing pain signals, oxytocin binds to opioid receptors and stimulates endogenous opioid release in the brain.

In addition to relieving pain, oxytocin lowers serum cortisol and can produce a calming effect and improve mood.

"It has the effect of making people happy, making them feel a little less anxious," said Dr Pedersen. "It changes the central nervous system; it makes the hypothalamus pump out chemicals that are telling the body it's okay, calm down."

Oxytocin can block "anticipatory pain," added Dr Pedersen. Patients with intractable pain are constantly waiting for "the next burse of pain" so are "in constant stress," she said.

However, when they take oxytocin, "they may actually get a lot of relief based on the fact that they are no longer having that anticipation."

Pain Free, No Side Effects

The investigators are working to determine optimal doses and routes of administration for oxytocin. They have experimented with combining oxytocin with low-dose naltrexone, benzodiazepines, neuropathic agents, opioids, and now ketamine, an N-methyl-D-aspartic acid receptor antagonist.

There has been a resurgence of interest in ketamine as a possible therapy for chronic pain conditions, including neuropathic pain, complex regional pain syndrome, fibromyalgia, postherpetic neuralgia, migraines, and spinal cord injury. 

At relatively high doses, ketamine has significant psychomimetic and euphoric properties that have led to abuse. Oral ketamine, sometimes called Special K, has become a popular nightclub drug.

Dr Tennant and Dr Pedersen have been experimenting with low-dose ketamine added to oxytocin in patients with the most severe intractable pain.

The study they presented at the AIPM meeting included five such patients (mean age, about 40 years) who had used oxycodone, morphine, hydrocodone, or hydromorphone for over a year.

Patients had not taken their short-acting opiate for several hours when they received 0.5 mL (2 mg — half of a syringe, or 20 units) of liquid oxytocin sublingually. Within 10 minutes, all five patients reported varying degrees of pain relief.

About 15 minutes after receiving the oxytocin, patients then received 0.25 to 0.50 mL (12.5 to 25 mg) of liquid ketamine, also sublingually.

The ketamine enhanced the pain relief. With the combination, two patients became completely pain free. These patients would "positively not" have been pain free with opioids, said Dr Pedersen.

The pain relief lasted about 4 hours with no side effects.

The Worst of the Worst

Dr Pedersen said the study patients were "the very worst" of pain patients. In her clinic, many patients suffer intractable pain — pain that never completely goes away with surgery or with drugs. "Some have had, say, seven or eight back surgeries and they have so much inflammation in their spine."

Some are battling an autoimmune disease, such as lupus. Others have arachnoiditis, an incurable inflammatory condition of the arachnoid mater, the middle layer of the meninges.

Because oxytocin is a hormone, its pain-relieving ability varies from patient to patient and its effectiveness is related, among other things, to blood levels, pain severity, and sex. 

In her experience, Dr Pedersen has found that men tend to have a better response to the combination of oxytocin and ketamine than women.

But women also respond "fabulously," she said. She described one 38-year-old female patient in her practice with a disc herniation who had been taking opioids, which were not helping her much. "She stopped taking them when she started using this combination therapy."

Other patients have been able to cut back on opioids "significantly enough that if they had to stop taking them, they would be okay," said Dr Pedersen.

The combination therapy may also address the issue of addiction, said Dr Pedersen. Some of her patients had become addicted to opioids, but after using the oxytocin-ketamine regimen, they're not craving or abusing opioids.

The liquid form taken sublingually provides "the best delivery system" and is much more effective than pills, said Dr Pedersen.

Although liquid oxytocin typically has a shelf life of only about 10 days, Dr Pedersen has found pharmacies that put the hormone in a suspension that lasts for 3 months.

Intriguing Results

Commenting on the research for Medscape Medical News, Charles E. Argoff, MD, professor of neurology, and director, Comprehensive Pain Center, Albany Medical College, New York, said it "provides intriguing results."

However, he said, a single-center open-label study of only five patients "is insufficient to draw any conclusions."

While the use of oxytocin as an analgesic is supported by basic science, "this study does not add significantly to the human studies already completed, given its size and design," said Dr Argoff.

Adding ketamine "dampens enthusiasm" for this therapeutic approach because of concerns about dependency and side effects, said Dr Argoff.

Adverse effects of ketamine can include nausea, headaches, fatigue, and dysphoria.

The authors have disclosed no relevant financial relationships.

Academy of Integrative Pain Management (AIPM) 28th Annual Meeting. Abstract 24. Presented October 21, 2017. 

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Cite this: Unique Drug Combo Promising for Severe, Intractable Pain - Medscape - Oct 31, 2017.